It’s Australia, it’s summer and it’s hot. Three indisputable facts. It took until 1998 before Australian Open officials came up with the first formal extreme heat policy, making the Open the only major tournament in the world to have such a policy. Basically, an extreme heat policy gives a tournament referee specific medical guidance on when to stipulate extended breaks or when it is simply too hot for players to continue with the stadium roof open. Under the Open's new heat policy, category five is the danger zone when, as Dr Broderick puts it, “the risk of heat-related illness significantly increases”. Play will be suspended, allowing for the retractable roofs to be closed on the three main courts. A 10-minute break between the third and fourth sets is new for men's tennis in 2019. (Women's tennis already had an extended break between the second and third sets under previous heat policies.) Dr Broderick says the algorithm behind the heat stress scale “takes advantage of the latest medical research into the effects of heat on the human body including the maximum heat stress an athlete can safely withstand, the sweat rate of that person and their core temperature. “The scale also accounts for the physiological variances between adults, wheelchair and junior athletes while also taking into account the four climate factors – air temperature, radiant heat [including from surfaces such as the ground] or the strength of the sun, humidity and wind speed.” This means an air temperature reading of 40 degrees won’t necessarily mean the heat policy comes into play. Players will be sweating profusely in that temperature range, but, crucially, the conditions must be safe enough for that sweat to also evaporate and maintain core temperatures at the right level. Humidity is the big factor. “If we have 40 degrees,” says Tennis Australia chief operating officer Tom Larner, “but low humidity, high wind, cloudy conditions, it may be that play continues – but if we have 40 degrees with high humidity and no wind and sunshine, it’s likely under that scenario that we would hit [a score of] five [and play would be suspended].” Reflected radiation from surfaces such as the court will be measured as a “black globe” temperature. Tournament director Craig Tiley says the new scale, generated from five different “weather stations” across Melbourne Park, will provide better data in real time and give players predictability so they can “put their own strategies [about dealing with the heat] in place”. Meanwhile, officials have concluded that previous decisions about implementing or not implementing the extreme heat policy at times of oppressive heat would have been backed up by the new scale. Says Tiley: “One of the first things we did on the outcome of that data was to do an overlay of decisions that we’ve made over the past five years. It was aligned to all the decisions we made were correct under this new policy. “Our decisions would have been correct.” The Age

It took until 1998 before Australian Open officials came up with the first formal extreme heat policy, making the Open the only major tournament in the world to have such a policy.

Basically, an extreme heat policy gives a tournament referee specific medical guidance on when to stipulate extended breaks or when it is simply too hot for players to continue with the stadium roof open.

How will organisers deal with the heat?

Under the Open's new heat policy, category five is the danger zone when, as Dr Broderick puts it, “the risk of heat-related illness significantly increases”. Play will be suspended, allowing for the retractable roofs to be closed on the three main courts. A 10-minute break between the third and fourth sets is new for men's tennis in 2019. (Women's tennis already had an extended break between the second and third sets under previous heat policies.)

Dr Broderick says the algorithm behind the heat stress scale “takes advantage of the latest medical research into the effects of heat on the human body including the maximum heat stress an athlete can safely withstand, the sweat rate of that person and their core temperature.

“The scale also accounts for the physiological variances between adults, wheelchair and junior athletes while also taking into account the four climate factors – air temperature, radiant heat [including from surfaces such as the ground] or the strength of the sun, humidity and wind speed.”

This means an air temperature reading of 40 degrees won’t necessarily mean the heat policy comes into play. Players will be sweating profusely in that temperature range, but, crucially, the conditions must be safe enough for that sweat to also evaporate and maintain core temperatures at the right level. Humidity is the big factor.

“If we have 40 degrees,” says Tennis Australia chief operating officer Tom Larner, “but low humidity, high wind, cloudy conditions, it may be that play continues – but if we have 40 degrees with high humidity and no wind and sunshine, it’s likely under that scenario that we would hit [a score of] five [and play would be suspended].”

Reflected radiation from surfaces such as the court will be measured as a “black globe” temperature.

Tournament director Craig Tiley says the new scale, generated from five different “weather stations” across Melbourne Park, will provide better data in real time and give players predictability so they can “put their own strategies [about dealing with the heat] in place”.

Meanwhile, officials have concluded that previous decisions about implementing or not implementing the extreme heat policy at times of oppressive heat would have been backed up by the new scale.

Says Tiley: “One of the first things we did on the outcome of that data was to do an overlay of decisions that we’ve made over the past five years. It was aligned to all the decisions we made were correct under this new policy.